When the Francis Scott Key Bridge was built in the 1970s, it was intended to relieve congestion from the Baltimore Harbor Tunnel.

Forty-seven years later, some of that traffic will be diverted back to the tunnel after the bridge collapsed last week upon being struck by a giant cargo ship, killing six construction workers. With the rebuilding process expected to take several years, that most likely means years of gridlock for commuters, travelers and truck drivers.

The flow of traffic through and around the city is taking on new patterns and shapes, as the 35,000 cars and trucks that once crossed the Key Bridge’s four lanes try alternative routes. The 1.6-mile bridge was the final link on Interstate 695, which loops around the city and is known as the Baltimore Beltway. The crossing’s overall structure, including its connecting approaches, was almost 11 miles long.

The bridge, a major north-south artery in one of the nation’s busiest ports, had connected working-class communities on either side, and it was used mainly by commuters. A former mayor called it the city’s “blue-collar bridge.”

Most of its local drivers will merge with some of the out-of-town drivers traversing the city through the Harbor Tunnel, on Interstate 895, and the Fort McHenry Tunnel, on Interstate 95, underneath the city’s harbor and closer to Baltimore’s downtown.